1. Technical Field
The embodiments herein generally relate to semiconductor processing, and, more particularly, to a system and method of gas distribution in semiconductor processing.
2. Description of the Related Art
Chemical Vapor Deposition (CVD) is a vapor based deposition process commonly used to deposit layers of material in a semiconductor manufacturing process. For example, CVD is used for the formation of dielectric layers, conductive layers, semiconducting layers, liners, barriers, adhesion layers, seed layers, stress layers, and fill layers. CVD is typically a thermally driven process whereby a deposition material (e.g., precursor flux) is pre-mixed and tailored to the substrate surface that the deposition material will be deposited upon. CVD requires control of the substrate temperature and the incoming deposition material to achieve desired film material properties and thickness uniformity. Derivatives of CVD based processes include but are not limited to Plasma Enhanced Chemical Vapor Deposition (PECVD), High-Density Plasma Chemical Vapor Deposition (HDP-CVD), Sub-Atmospheric Chemical Vapor Deposition (SACVD), laser assisted/induced CVD, and ion assisted/induced CVD.
As device geometries shrink and associated film thickness decrease, there is an increasing need for improved control of the deposited layers. A variant of CVD that enables superior step coverage, materials property, and film thickness control is a sequential deposition technique known as Atomic Layer Deposition (ALD). ALD is a multi-step, self-limiting process that includes the use of at least two deposition materials (e.g., precursor fluxes or reagents). Generally, a first deposition material is introduced into a processing chamber containing a substrate and adsorbs on the surface of the substrate. The excess first deposition material is purged and/or pumped away. A second deposition material is then introduced into the chamber and reacts with the initially adsorbed layer to form a deposited layer via a deposition reaction. The deposition reaction is self-limiting in that the reaction terminates once the initially adsorbed layer is consumed by the second deposition material. The excess second deposition material is purged and/or pumped away. The aforementioned steps constitute one deposition or ALD “cycle.” The process is repeated to form the next layer, with the number of cycles determining the total deposited film thickness. Different sets of deposition materials can also be chosen to form nano-composites comprised of differing material compositions. Derivatives of ALD include but are not limited to Plasma Enhanced Atomic Layer Deposition (PEALD), radical assisted/enhanced ALD, laser assisted/induced ALD, and ion assisted/induced ALD.
Presently, conventional vapor-based processes such as CVD and ALD are designed to process uniformly across a full wafer. The ability to process uniformly across a monolithic substrate and/or across a series of monolithic substrates is advantageous for manufacturing efficiency and cost effectiveness, as well as repeatability and control. However, uniform processing across an entire substrate can be disadvantageous when optimizing, qualifying, or investigating new materials, new processes, and/or new process sequence integration schemes, since the entire substrate is nominally made the same using the same materials, processes, and process sequence integration scheme.
In conventional processing systems, when optimizing, qualifying, or investigating new materials, new processes, and/or new process sequence integration schemes, a combinatorial approach may be taken where each processed substrate generally represents, in essence, only one possible variation per substrate. For examples, in a conventional combinatorial approach, numerous material compositions may be systematically explored during a screening process, and the results of this screening process are used to filter materials into subsequent screening processes. With only one possible variation per substrate, however, fewer data points per substrate are gathered resulting in longer times to accumulate a wide variety of data and higher costs associated with obtaining such data. Moreover, when conventional systems simply try to add more than one possible variation to a substrate, conventional deposition material distribution systems are unable to evenly deliver and deposit the different materials to a single substrate. What is needed, therefore, is a symmetrical distribution system that can distribute multiple deposition gases to specific sections on a substrate.